Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$230.70	9.851%	$253.4263	$253.43	$253.45	$253.40
Purchase #2	$217.52	6.367%	$231.3695	$231.37	$231.35	$231.40
Purchase #3	$99.42	11.105%	$110.4606	$110.46	$110.45	$110.50
Purchase #4	$35.52	7.424%	$38.157	$38.16	$38.15	$38.20
Purchase #5	$48.72	3.316%	$50.3356	$50.34	$50.35	$50.30
Purchase #6	$209.43	10.580%	$231.5877	$231.59	$231.60	$231.60
Purchase #7	$222.73	4.220%	$232.1292	$232.13	$232.15	$232.10
7 purchase totals =	$1,064.04		$1,147.4659	$1,147.48	$1,147.50	$1,147.50